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Tob. Sci., 1992, 36-02, p. 6-7, ISSN. 0082-4523, Tob. Reporter, 1992, 119-1, p. 61-2

Evaluation of an enzyme-linked immunosorbent assay for Phytophthora parasitica var. Nicotianae in tobacco

CSINOS A.S.; MILLER S.
Department of Plant Pathology, Coastal Plain Experiment Station, Tifton, GA, USA; Agri-Diagnostics Associates, Cinnaminson, NJ, USA; Ohio State University, Department of Plant Pathology, Wooster, Ohio, USA

Diseased tobacco (Nicotiana tabacum L.) samples collected from a black shank nursery or commercial fields in 1988 and 1989 were used to compare enzyme-linked immunosorbent assay (ELISA) Phytophthora kits to standard culture plating identification techniques (CID) for Phytophthora parasitica var. nicotianae. Each of the samples tested was tentatively identified as black shank based on symptoms and field history. The immunoassays were double antibody sandwich ELlSAs. A “dipstick’ ELISA test was evaluated in 1988, and the Alert™ , “D” On-Site Assay, ELISA was used in 1989. Stronger ELISA reactions were obtained from pith tissue in stem lesions than from rhizosphere soil or infected roots. In 1988, all of the 39 samples tested positive for Phytophthora with the ELISA “dipstick,” whereas the CID technique only detected Phytophthora in 76.9% of the samples. Three of the 39 samples were identified as Phytophthora by CID, but were negative by ELISA, and 9 of 39 samples were identified for Phytophthora by ELISA but did not yield cultures. In 1989, 29 of 55 samples evaluated were diagnosed as black shank by both Alert™ Phytophthora Assay ELISA test kit and by the CID technique. Two of the 55 samples were identified as Phytophthora by CID techniques but were negative by ELISA, and 8 of 55 samples were positive by ELISA but negative by the CID technique. The Alert™ test was quick and very comparable in diagnoses to CID techniques.